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Cleaning sink plug holes and drains

You may well have seen plenty of 'how to' videos on the internet about unblocking sink plug holes and drains. One of the (visually) more interesting tips is to pour bicarbonate of soda or baking soda down the plug hole and then add white vinegar and watch the fizzing fun begin! You may also remember from chemistry class that bicarb is alkali and vinegar is acid. So the reaction you are seeing is the two effectively neutralising each other. So is it actually helping?

The answer in a roundabout way is 'yes'. But......there's a much better solution. Our MD (and qualified chemist) Bruce Maxwell explains:

"Adding vinegar and bicarb will fizz like crazy and the physical action will knock around debris.  The bubbles will do a bit of cleaning, but bicarb is not a great cleaner for sink drains as its pH is too low – it would be better to use a stronger alkali such as Soda Crystals with hot water. This will react with any fats and oils that are restricting the pipe, and make them water soluble, and flush away with the other matter that is causing odours and/or restricted flow. Adding vinegar after a good soak in Soda Crystals will fizz and make sure everything is knocked off the pipe walls."

Remember, prevention is better than cure! Once a pipe is TOTALLY blocked, your best options are plunging and rodding. We don't like to recommend toxic products like caustic soda (not to be confused with Soda Crystals) for obvious reasons. Put a mugful of Soda Crystals and hot water down your drains each week and you shouldn't have a problem. They are biodegradable and can even be used in houses with septic tanks.

NB. Do not use soda crystals or liquid soda crystals on aluminium or lacquered surfaces.

27 thoughts on “Cleaning sink plug holes and drains

  1. my bathroom sink is really blocked. how much soda crystals should i use and how long should i leave them before adding vinegar and then flushing with hot water?

    1. Is the water draining but slowly? If it’s not even draining, then it may be totally blocked and plunging should be your first action. Remember to block the overflow drain hole with a cloth and hold it in place. Get someone else to help if needed.

      If it is draining, albeit slowly, try putting half a bag of Soda Crystals into the basin with just enough boiling water to wet all the crystals. Leave to slowly sink down the hole, adding more small amounts of boiling water as needed to keep them going down the hole. Once the speed of draining increases, keep putting some more boiling water and Soda Crystals down the sink until the blockage has been removed and the material moved away to the main sewer.

      The use Soda Crystals regularly to prevent it happening again.

  2. Are soda crystals safe to use with a septic tank / cess pit? We have to be really careful what we use but I can’t seem to find out if soda crystals would be a option.

  3. Can I use Soda Crystals to degrease my dishwasher, branded cleaners are expensive and I have not found them very effective.

  4. Can I use soda crystals to clean the bathroom basin waste and shower waste as I have a Saniflo pump system and the pipes occasionally get blocked with accumulated hair and soaps/ conditioner?

    1. Hi Sue – yes they’re fine. The only metals Soda Crystals shouldn’t be used with are aluminium, zinc and copper/

  5. I am wondering if there was a way to use bi carb to keep the water in a hot tub clean rather than chemicals.

    1. Hi Annie – Soda Crystals would be better for cleaning (assuming there are no aluminium, zinc or copper parts) but it would be advisable to check with the hot tub manufacturer.

  6. Hi,, we have a spa bath and wondering if it would be possible to use soda crystals to clean the system? Thanks ms in advance

    1. Yes – they are ideal. Just check with the manual or manufacturer that there are no aluminium, zinc or copper components to be safe (which there shouldn’t be).

      You can now get 1.5kg bags from Wilko (own brand) and Waitrose (DP brand) for heavier use applications like this.



    1. In theory, you certainly can, but in practice it will have limited benefit for cleaning. The acid and alkali are simply reacting with each other and neutralising.

  7. Is it safe to pour soda crystals down the kitchen sink followed by a kettle full of boiling water, or could it damage the plastic pipes and joints? Thanks for your assistance.

    1. Hi Susan – yes it’s fine. The water will start to cool as soon as it hits the sink and drains. Soda crystals and very hot water are ideal for dissolving grease. Use boiling water and then after a minute run the hot tap for a minute so that all greasy residue is sluiced down the pipes to the main sewer system. HOWEVER, do try to remove as much solid fat from pans before washing them. Otherwise sewerage systems themselves can get blocked. Many water companies will give you a free fat trap, so that you put less fat down the drains.

  8. There is a same problem here, but water is accumulated in the kitchen sink and don’t move. Is this a wise solution to use baking soda/vinegar or soda crystals/hot water?

    1. If the water simply isn’t moving, a plunger should normally clear the blockage. Remember to block the overflow hole before plunging. Once the water is starting to drain, follow the instructions using Soda Crystals and hot water.

  9. What is the best way to use soda crystals in a wash-hand basin with a spring-loaded pop-up plug which doesn’t seem to be removable?

    1. Dissolve the Soda Crystals in hot water and fill the sink. They open the plug hole and let the solution drain. If it drains very slowly, you have an obstruction. Either try plunging after the solution has drained or repeat the process until water drains freely.

      Then run the hot water tap for 30 seconds or so until the sink drains.

    1. Hi – have you read the article? The message is that prevention is better than cure. If you’ve got a TOTAL blockage that Soda Crystals or a plunger aren’t sorting then you’ll have to resort to harsh chemicals (make sure you follow the health & safety guidance), rods, or a plumber.

      You may want to read the comment from Glenn Miller at the bottom of this page.

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